IGPP/LANL
Field Data
Magnetic Field During a Quiet Period
Dayside Pc 3-4 Pulsations
The text above was taken from IGPP at UCLA @:
Ground-Based Magnetometer Array
Figure 3 shows the three components of the magnetic field measurement at San Gabriel Dam test site during a quiet period (top panel) and
their power spectra. The three
sensors 1, 2, and 3 are roughly in the north-south, east-west, and vertical direction, respectively. The average amplitude of the noise level is smaller than 0.1 nT
peak-to-peak. The noise level is comparable to that of magnetometers in AFGL chain at highest frequency (0.5 Hz) and much lower at low frequencies. Since the
magnetometers at AFGL chain had a much smaller dynamic range (+/- 64 nT), this system is approximately 100 times quieter at 100 sec periods than the AFGL circuitry
while maintains a dynamic range of +/- 5000 nT, almost 100 times greater than the AFGL units.
Figure 4 shows an example of Pc 3-4 waves observed at Los Alamos site Fenton Hill site (LANL). The waves with a peak-to-peak amplitude of 0.2 nT can be easily seen
by the magnetometer. The power of the wave at its peak frequency is two orders of magnitude higher than the noise power.
http://www-ssc.igpp.ucla.edu/uclamag/posters/agu98s/
